A myriad of low-carb products are marketed as having “zero net carbs”, but a closer look at the nutrition label reveals most of the “cancelled” carbs to be from dietary fiber or sugar alcohols. What does this wizardry mean for calorie and carbohydrate counters? Not as much as the marketing would have you believe.

A Quick Primer On Fiber and Sugar Alcohols

Most nutrition labels, in particular those in America, lump all carbohydrates—sugars, sugar alcohols, and fiber—together in the total carbohydrate count. So how do they differ from one another?

In case you’re wondering, sugar alcohols do occur naturally, but not in the huge amounts that you would find in “sugar-free” products; you’ve probably heard of some, such as xylitol, sorbitol, erythritol, and many other names ending with -tol. They mimic the sweetness of table sugar but usually have fewer calories than the real deal.

Advertisement

Despite many internet debates, fiber does have calories, depending on the classification of the fiber. Most sources might say that fiber contains “negative calories” because the body lacks the digestive enzymes to break them down into usable energy, but bacteria in the large intestine can convert some fiber into available energy (in the form of short-chain fatty acids), putting the caloric value anywhere between 1.5- to 2.5-ish calories per gram depending on the type—there’s simply no hard consensus on this. Meanwhile, the calories of sugar alcohol hover between 1.5 to 3 calories per gram, also depending on the type of sugar alcohol.

So, neither fiber nor sugar alcohol is truly a zero-calorie food. However, in everyday realistic amounts, the calories from either are so trivial that they’re not worth fretting over. We’ve written before about “free foods”, which you can eat in reasonable amounts without needing to closely track your intake, if you do. But you shouldn’t ignorethem completely, thinking that the calories are merely disappearing into the ether (although some can very well disappear in your poop if you’re eating high amounts of fiber).

So, What Is a Net Carb?

Net carbs are defined by total carbohydrates minus dietary fiber and sugar alcohols. Net carbs also go by other names: “impact” carbs or “effective” carbs. Currently, the Food and Drug Administration has yet to establish any solid guidelines for the low-carbness of a food in order for the manufacturer to legally state that their food is indeed low-carb.

Advertisement

In other words, manufacturers can say what they want, except explicitly state that a food is low-carb.

This labeling of effective carbs makes some sense for diabetics since they must control carbohydrate intake—specifically, the refined sugar type that rapidly raises blood sugar—for health reasons. Typically, diabetics must differentiate between the types of carbohydrates a food contains to determine what amount of the total carbs will actually impact their blood sugar.

Fiber and sugar alcohols interact in the body differently. In particular, most sugar alcohols are not (fully) digested and absorbed the same way sugary or starchy carbohydrates are, and so have a comparatively lesser—but still present—impact on blood sugar.

Fiber is special because it positively impacts blood glucose through a combination of a few things: first, it somewhat blocks absorption of carbohydrates (and other nutrients, including protein and fat), which ultimately reduces the total number of calories absorbed by the body if fiber is eaten in large amounts; second, it delays gastric emptying, which is a fancy way to say that food leaves your stomach more slowly. When that happens, you avoid large spikes in blood glucose, which normally occurs when you eat something fast-digesting like a Kit-Kat.

The Marketing Trap

In the midst of this low-carb craze for weight loss, you’ll see many normally carb-heavy food items, such as bread or tortillas, that claim “only such-and-such net carbs.” The mention of net carbs is the food manufacturer’s effectively discounting fiber and sugar alcohols as true carbohydrates, because of their aforementioned less dramatic impact on blood sugar. Hence, you may even see “zero net carbs” in some cases.

Advertisement

Therein lies a very sour pickle. For diabetics, the labeling can be misleading since they should not completely discount all sugar alcohols from the total carbohydrate count. Dietitians recommend that they count sugar alcohols at half the value of the food’s total carbohydrate content. For example, if a food contains 18 grams of sugar alcohols, they are advised to count 9 grams of them as effective carbs.

The other problem here is similar to the phenomenon we witnessed with the whole reduced fat and fat-free craze back in the 90s: people may think it’s okay to ignore the other carbs altogether and overeat due to the halo effect of these foods—if they appear to be healthier, it’s okay to eat more!

If you’re choosing a sugar-free or low-carb version of something because you think they’re more calorie-friendly, think again. They can still contribute a significant amount of calories when consuming the food as a whole. In the case of foods with sugar alcohols, these foods—albeit labeled as “sugar-free”—typically contain more fat. Sometimes when you compare the regular version and the sugar-free version, you may even discover the latter to actually contain more calories than, or about the same as, the regular version.

The bottom line: “net carbs” and all variations of the term are an advertising gimmick and shouldn’t be fully trusted as their keeping your health (or waistline) in mind.

Don’t sweat the difference between the amount of soluble and insoluble fiber eaten either. While you can subtract fiber carbs from your total, it’s much more trouble than it’s worth. Realistically, many of us, especially those on a Western diet, don’t eat enough fiber-rich foods to worry about it (we’re talking 50 to 100 grams of fiber here). At the end of the day, 100% nutritional accuracy is a neurotic exercise in anal-retentiveness that may be helpful for a tiny percentage of the population, such as very, very lean folks who are perhaps preparing for a competition.

When you include all carbohydrates, you can more effectively plan out your meals and facilitate your weight loss as well. Because if you are misled by the whole “net carbs” thing, that could mean you’ve made a whole bunch of calories left unaccounted for, which could be the reason you are not losing weight, or perhaps even gaining weight!

Advertisement

Regardless, you can eat the foods that advertise “zero net carbs” if you’d like, but don’t be fooled into thinking that they’re necessarily better for you or magically help you manage your weight better.

Stephanie Lee is a geeky health and fitness freelance writer. You can follow her shenanigans on Twitter or on her YouTube channel.